Nobody really knows what happened to Butch Cassidy and the Sundance Kid. Supposedly they were killed in a South American shootout in 1908, but the evidence is vague, and there are conflicting claims that at least Butch survived into his 70s. Grounded in that alternate history, "Blackthorn" imagines a scenario for Butch's later years and gives us a different kind of Western - somber, reflective and set in the elevated plains and salt flats of Bolivia.

It takes place in 1927. Sundance is dead. Etta is dead, and Butch, who goes by the name of Blackthorn, has a white beard. He has transformed from wisecracking Paul Newman into Sam Shepard, who doesn't joke much. By his early 40s, Shepard already carried an aura of deep, lived-in history, and by now he is like a living monument, who can just sit and say nothing and make you think, wow, this guy has seen things. So what better actor to play a notorious outlaw who has grown into his regrets and yet is still dangerous?

These days all Butch wants to do is cash out and go home. A horse dealer in Bolivia, he sells everything he's got with the intention of going back to America and seeing Etta's son, who is also Sundance's son - or maybe Butch's - see, this is why they called it the Wild West. But something keeps him in Bolivia and throws him together with a Spanish thief, played by Eduardo Noriega - who looks like a young, healthy Marcello Mastroianni.

The film's central adventure involves the men's effort to retrieve $50,000 and escape the country. This caper aspect is enough to keep the narrative chugging along, but the film's main appeal comes from character interaction and the movie's exploration of Butch's moral nature, which is also revealed in a series of flashbacks. It's a funny thing how modern 1927 can look after a quick visit to 1900 - and that sense of modernity emphasizes Butch's dislocation. He's a man from the previous century, and anyone who feels a few beats behind today's technology might easily identify.

Miguel Barros' screenplay doesn't look back or build on the 1969 "Butch Cassidy and the Sundance Kid." But it does throw in one reference that's irresistible if you catch it. At one point, as six horsemen are gaining on them, Blackthorn turns to the Spaniard and advises they dash out into the desert. "The desert will kill you before they do," he says. Get it?